A nursery in Ranchi has 136 neem saplings and 306 ashoka saplings. They are planted in rows so that every row holds saplings of only one kind and every row holds the same number of saplings.
What is the least number of rows needed?

To use the fewest rows, each row must hold as many saplings as possible, namely HCF(136, 306). Since $136=2^3\times$ 17 and $306=2\times 3^2\times$ 17, HCF = $2\times 17=34$. That gives 136 / 34 = 4 rows of neem and 306 / 34 = 9 rows of ashoka, so 13 rows in all. Answering 34 gives the row size, not the number of rows; 4 counts only the neem rows; 26 comes from using 17 instead of 34 as the row size.